1. Field of the Invention
This invention relates to a disengageable coupling comprising a first coupling part affording a bore and a second coupling part which is insertable into the bore in the first coupling part, a frictional connection between the first and second coupling parts being established by expanding the second coupling part by fluid pressure into engagement with the first coupling part.
2. Prior Art
In one previously proposed form or coupling (US-PS 2720735), two interfitting coupling parts have a hose inserted in helical configuration between them, and by internally pressurising the hose it is engaged with the two coupling parts so as to be able to transmit torque between them. The disadvantage of such a design is that the hose itself takes part in the torque transmission, and the material thereof is subject to high loads.
A further design of coupling proposed in US-PS 4428737 has, interposed between a shaft and a hub, a coupling sleeve which is in the form of a number of joined I-section annular strips providing annular chambers for receiving fluid under pressure. However, the sleeve itself transmits torque between the shaft and hub and leakage is possible in the welded joint between the annular strips. A further disadvantage is that the coupling requires to be of large dimensions.